Eric, I join your guess... I have seen the picture an dit was the first thing that came to my mind, then decided to read the whole thread before giving my opinion, and found you came already to the same conclusion... Even though I must admit I have never seen a cycnoches alba before, the shape of that plant is to close to cyc. loddigesii and to far from Cyc. chlorochilon...
way to go!
I would suggest you to contact the UAO (Unión Aficionados a las Orquídeas Informes 4791-8670 4854-1086), the Sociedad Argentina de Botanica
Boletín de la Sociedad Argentina de Botánica - Maevia Noemí Correa (1914-2005) (contact details at the botton of the previous link) or the Club Peruano de Orquideas
Club Peruano de Orquídeas [Las Orquídeas] they can provide you better information regarding this 'alba' plant. They should be better informed about the available clons in Argentina.